Probably a simple question but one I cannot figure out from the books:

Some power and attack cards have at the HIT statement a small symbol saying 1[W], or 2[W] at level 21. For example:

How do I read the 2[W]? Is it 2 times the weapon? does someone need to roll 2 d20 checks? I understand this is probably for the higher levels but my players ask questions alot and I just want to be prepared. :)

As in the example it gives: if the weapon you're using for this power is a regular dagger, your damage dice is 1d4. If a power instructs you to roll 2[W], you roll twice that. For a dagger, that means 2d4.

If you're still getting used to the combat system and powers (i.e. most things you will use often), there's a few sections you should liberally refer to:

The Combat chapter, on PHB page 264.

The How to read a power section, which is located right near the beginning of the Classes chapter (since that's where all the powers are) and begins at page 54.

Also, equipment blocks (or equipment cards) aren't quite the same as power blocks (and cards). They're explained in the Equipment chapter, right at the beginning of the Magic items section, under the heading Reading a Magic Item on page 224.

The "at level 21" bit means your power upgrades at level 21. A lot of at-wills do this (and so do some other powers), because they'll be with you the whole way and had better not get outdated. From levels 1 to 20, you'll be rolling 1[W] for damage, but as of level 21, you'll roll 2[W] instead. (That's the "increase damage to" bit.)